3D printing of high strength-to-weight ratio ultra-high temperature ceramics (UHTCs) with multiscale porosity
Abstract
3D printing of high strength-to-weight ratio ultra-high temperature ceramics(UHTCs) with multiscale porosityCeramic materials used in ultra-high temperature applications such as in hypersonic vehicles are not only required to exhibit low thermal conductivity, but also need to comply with both weight and strength requirements to provide for efficient in-service use. Porous ceramics and scaffold structures an address such requirements to certain levels, however, combining these via 3D printing ceramic foam pastes into scaffold structures could provide a method for creating complex shaped ceramics with high performance-designed structures. This work will develop foundation process-property-structure relationships for scaffold structures made with porous struts of ultra-high temperature ceramic (UHTC) using extrusion based 3D printing techniques. Controlling particle interactions in a colloidal suspension is key to producing pastes suitable for the direct ink writing (DIW) 3D printing technique. We will establish which additives, solids loadings and foaming techniques produce paste inks with the suitable bubble size distribution and flow properties. This will include studying the flow properties including; viscosity and shear yield stress that will aid in determining the suitability and limits of the UHTC pastes for this extrusion technique.In addition to the process development just mentioned, the current proposal will evaluate the mechanical behavior of the structures. Mechanical properties of such 3D printed porous ceramics will be measured in 4 points bending which has not been published anywhere in the world at the time of writing. Comparison of the strengthto-density ratio of samples produced via conventional techniques as well as via the new 3D printing technology will be conducted. Specifically, to compare: 1) a dense ZrB2, produced by slip casting; 2) a lattice structureproduced by 3D printing with dense struts; 3) a lattice structure produced by 3D printing with porous struts.The technical approach will consist of seven main stages; 1. A detailed review of the literature related to multi scaled porous ceramic structures that are currentlyproduced by additive manufacturing. 2. Determine optimized formulations with selected additives for use the UHTC materials used in this project (ZrB2). Additives may include: i) dispersants to produce stable suspensions, ii) binders that are required to increase the green strength of the ceramic, and iii) surfactants that render the surfaces of the particles weakly hydrophobic allowing them to absorb at a gas or liquid (in the case of an emulsion) interface.3. Mechanical foaming methods and tools that result in stable foams and the required bubble size distribution will be established. 4. Detailed flow property measurements will be carried out with the sample materials at key stages duringthe processing, i.e., from the dispersed stage through to the foaming stage. This will provide data to ensure repeatability throughout the processing stages as well as changes in the particle interactions caused by the different additives. The data obtained at this stage is key to producing foams that meet the requirements for good printability. 5. Printing parameters for the UHTC foams will be established via experimental techniques. Traverse speeds, offset distances, extrusion force or pressure and layer height are among some of the parametersthat need to be optimized to print reproducible structures. 6. Ascertain drying and firing conditions that result in complete multi-scale porous ceramic structures.7. Evaluate the mechanical properties via compressive strength and 4-point bend measurements to reveal the relationship between the morphology and amount of porosity and the mechanical strength. If successful, this project could aid in the development of complex shaped ceramics for ultra-high temperaturethermal protection systems with high strength to weight ratios.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 27, 2018
- Source ID
- N000141812680
Entities
People
- George V Franks
Organizations
- Office of Naval Research
- United States Navy
- University of Melbourne